Istems

Istems (often written i-stems) is a term used in some linguistic grammars to describe a class of word stems characterized by the appearance or retention of an i vowel in the stem during inflection. The label is not universal; its definition and membership vary by language and author, and what looks like an i-stem in one language may be treated as another stem class in another.

In historical and descriptive grammars, i-stems are invoked to explain irregular vowel alternations in certain nouns and adjectives. The defining feature is that the stem, rather than the suffix alone, influences inflection by supplying or sustaining the vowel i in some forms, especially in oblique cases or in the genitive.

In Latin, some grammars describe a subset of nouns as i-stems because they display stem alterations when declined; in others these nouns are simply categorized under standard declensions. In Sanskrit, i-stems refer to nouns whose stems end in -i and participate in a distinct set of endings; in other languages with vowel alternation, the term is used similarly with language-specific details.

Because the concept is not uniformly adopted and is heavily dependent on scholarly tradition, modern grammars often prefer explicit paradigm tables and language-specific terminology (for example, a-stems, i-stems, u-stems in Sanskrit). This helps avoid ambiguity when describing stem-based inflection.

See also: stem, inflection, morphology, stem class.